He says the days leading up to Rosh Hashanah are generally a very good time to buy American and Israeli shares. Mr Ralph explains: "If you buy shares two days before Rosh Hashanah and sell them the day after, then you make an average return of just over one per cent. So, it's a one per cent return in just four trading days.

"If you can repeat that a few times a year, then you're doing very nicely," says Mr Ralph, who has been with the publication for the past eight years.

Why Rosh Hashanah? "The Jewish community has a fairly prominent role in the financial markets, and if people are looking forward to something, as they might be at Rosh Hashanah, and feeling quite confident and uplifted, then they are more likely to buy shares. And if more people buy shares on those days, the share prices are going to rise."

Conversely, Yom Kippur, he says, is a bad time to buy but a good time to sell. "If you sell your shares the day before Yom Kippur and buy them back the day after - then you would make an average return of 0.35 per cent. Not quite as good as the Rosh Hashanah strategy but still a decent return from one day."

The reason? "Because people are feeling quite apprehensive or downbeat, they might decide not to get involved in the financial markets, so there is a record of the markets not doing so well over Yom Kippur."

His theories are based on research compiled by his colleague Simon Thompson for Mr Thompson's book Trading Secrets, to be published in mid-December. It traces the best days to invest.

Other historically profitable days to invest are St Patrick's Day, which usually falls towards the end of March, and a Friday the 13th. "Buying shares a couple of days before St Patrick's Day and selling the day after also shows around a one per cent return." This is due to the Irish community in the US. "If they're confident and excited for St Patrick's Day, then they will be buying more shares."

As for Friday the 13th: "Friday in general is a good day for shares. People are looking forward to the weekend and tend to be quite confident. Plus, companies are less likely to put bad news out on a Friday, and Friday the 13th seems to be a particularly auspicious day."

Yet he acknowledges that investors face an anxious time in today's market. "A month ago it was unthinkable that so many global financial institutions would be forced to seek a government rescue, merge or go bust, but that is just what has happened. The problem for investors now is that there may be plenty more bad news to come out of the financial sector, and that the regulatory framework needs to be completely rethought. Until there's more clarity, the stockmarket is unlikely to make much progress. However, there are some reasons to be hopeful for the long term. The Bank of England may start to cut interest rates towards the end of the year, and that could provide the basis for a recovery in share prices."

And while acknowledging that everything seems to be going down at present, he says there is always money to be made, whatever the trading conditions.

"There is a history in this country of housing booms and busts, which give quite a good indication of where we should invest when house prices fall. Given that house prices are down about ten or 11 per cent over the past 12 months, and they're still falling - it's a trend that's going to continue for another two or three years and might fall another 17 per cent from here - then there are some quite good places to invest."

Promising sectors, he says, include pharmaceuticals and tobacco. "Tobacco and pharmaceutical shares do badly when other more cyclical areas, such as media, technology and retail, look more exciting, but they are seen as a safe haven when things are going badly."

Sectors to avoid include government bonds and commodities, notably oil, gas and mining. Mr Ralph is also cautious about retailers. "Consumer confidence is very low and people are worried about house prices and job security." What about Marks & Spencer? "I would be wary. It's a great brand name, but the general retail environment isn't good."

He advises against tracking every stockmarket move. "With the growth of the internet, it's easy to see live share prices every day and be tempted. One of the biggest things that erodes value for investors is too-frequent trading, as you rack up the commission every time you make a trade."